All living organisms are built up by semiflexible polymers. To understand the fundamental functional principles that enable the active complexity of living systems, we have to explore and uncover the physics of this special polymer class to be able to precisely alter their exclusive mechanical properties.

Here we use DNA-based, bionic constructs to explore the rich phase space of entangled as well as crosslinked networks of semiflexible polymers. Using biomimetic DNA nanotubes with similar mechanical properties as actin, we are able to directly test and determine the influence of the stiffness of the underlying polymer on the overall network elasticity. In contrast to predominant theories of entangled semiflexible polymer networks, we show proof that these networks stiffen upon increasing the persistence length of the underlying filaments. I.e., these networks stiffen without changing the underlying mesh size of this hydrogel, which is an unavoidable side effect for current cell experiments based on collagen matrices.

In addition to these purely artificial systems, we also directly target actin networks to precisely influence their mechanical properties by introducing DNA-based crosslinkers. Although cells do employ crosslinking proteins, they can be hardly compared since they vary in many different parameters. Our constructs are readily tuneable and allow us, for instance, to explore the impact of a crosslinker’s binding affinity decoupled from any other parameters. Measurements with bulk rheology revealed that the bionic crosslinkers indeed recreate the mechanical fingerprints of naturally occurring crosslinkers such as fascin and show a non-trivial, concentration dependent stiffening of actin networks.